1. Field of the Invention
The present invention relates to a gasket holder, particularly to a gasket holder suitable for using in gas supply devices used in industrial manufacturing devices such as semiconductor manufacturing devices.
2. Description of Related Art
There have been conventionally used corrosive gases in etching or the like of photoresist fabrication in semiconductor manufacturing steps. Photoresist fabrication (photoresist coating, exposure, development, etching) is repeated at plural times in semiconductor manufacturing steps and therefore, gas supply devices for supplying corrosive gases as necessary are used in actual semiconductor manufacturing steps.
Meanwhile, in manufacturing steps of semiconductors in recent years, it is necessary to supply small amounts of corrosive gases or the like with an accuracy of 1% or less in respect of a flow rate and the requirement of accuracy becomes severer. Therefore, control valves having high accuracy and high response are widely used also in corrosive gas supply devices in semiconductor manufacturing devices. In such a flow rate control valve having high accuracy, slender pipes are used and accordingly, it is difficult to completely exclude corrosive gases remaining in the pipes.
However, when corrosive gases remain in pipes at the inside of the flow rate control valve, the inside of the pipe is corroded by the remaining corrosive gases, accuracy of a flow rate mass sensor is deteriorated and corrosive gases cannot be supplied with high accuracy which causes to significantly deteriorate the yield in semiconductor manufacturing steps.
Further, if the pipe is left with the remaining corrosive gas after once supplying the corrosive gas until next supply of the corrosive gas, metals or the like at the inside of the pipe is corroded by the remaining corrosive gas and when the corrosive gas is successively supplied, impurities such as particles or the like are mixed in the corrosive gas which adversely effect on semiconductor products.
Hence, the applicants devised a gas supply device disclosed in JP-A-6-241400 in order to solve the above-described problem. According to the gas supply device, as shown by FIG. 16, an input valve 102 and an output valve 103 for cutting off flow of a corrosive gas Fa, a flow rate control valve 105 for controlling the flow rate of the corrosive gas Fa at an intermediary between the input and output valves, a purge valve 106 for supplying a replacement gas to the flow rate control valve 105 and an ejector valve 107 connected to an ejector, not illustrated, for reducing pressure of the corrosive gas Fa inside of the flow rate control valve 105, are unitized, and the flow rate control valve 105 is fastened to direction change blocks 110 and 111 from above by screws 112 via flow rate control valve blocks 108 and 109. Here, gaskets 113 and gasket retainers 114 are used respectively between the flow rate control valve blocks 108 and 109 and the direction change blocks 110 and 111 for preventing leakage of the corrosive gas Fa. According to the gasket retainer 114, legs are formed by bending downwardly both ends thereof in the longitudinal direction and the gasket retainer 114 is fixed to the direction change block 110 or 111 by pinching the outer sides thereof by the couple of legs.
The corrosive gas Fa can be removed efficiently by constituting the gas supply device as described above and further, the flow rate control valve 105 can be integrated with the gas supply device from above while maintaining a gas tight state.
However, there are following problems in the above-described gas supply device.
(1) Positioning of the gasket retainers 114 is conducted by attachment bolts attached to the direction change blocks 110 and 111 and therefore, the gaskets 113 may not be accurately positioned to through holes. Further, the gaskets 113 are liable to shift from or detach from the direction change blocks 110 and 111. PA1 (2) The gaskets 113 are held by the gasket retainers 114 by two point support and therefore, the gaskets 113 are liable to detach from the gasket retainers 114.
The present invention resolves the above-described problems and it is an object of the present invention to provide a gasket holder facilitating attachment and detachment of the gasket holder, capable of preventing positional shift and detachment of the gasket holder in attaching and detaching a flow rate control valve and preventing a gasket from detaching from the gasket holder.